Malaria is the most important vector-borne disease in Southeast Asia. It is estimated that the region accounts for 30% of the global malaria morbidity and 8% of the global mortality. Malaria epidemiology in this region is characterized by high spatial and temporal heterogeneity in falciparum and vivax malaria incidences, and by the presence of diverse vector species with different vectorial capacities for the parasites. The sympatric occurrence of multiple vector species with distinct bionomics and vectorial capacity complicates our understanding of malaria transmission and hinders malaria control efforts. Currentiy, pyrethroid insecticide-treated nets and pyrethroid-based indoor residual spray are the primary vector control tools in the region. However, the evolution and spread of insecticide resistance and drug resistance reduce the efficacy of these tools. Therefore, understanding the vectorial system and developing new vector control and resistance monitoring tools are of paramount importance. The overarching objectives of this project are to understand the vectorial system in diverse ecological and epidemiological settings in China, Thailand and least studied Myanmar, and to develop new vector control tools to reduce malaria transmission. To achieve these objectives, we have developed five specific aims: 1) to determine community structure of malaria vectors and the impact of anthropogenic environmental changes on vector community structure; 2) to examine the populafion genefic structure and bionomics of major malaria vector species; 3) to develop new olfacfion-based tools for control and transmission surveillance of the major malaria vectors; 4) to examine the ufility of a new formulafion of microbial larvicide and entomopathogenic fungi for adult mosquito control; and 5) to determine pyrethroid resistance mechanisms and develop resistance monitoring tools for the major malaria vectors in the region. We anficipate the new knowledge and new tools from this project will greatly contribute to the malaria control program in Southeast Asia.